1. The Field of the Invention
The present invention is in the field of fire retardant and heat resistant yarns and fabrics, and other fibrous blends. More particularly, the present invention is in the field of yarns or fabrics that include metallic and/or other high strength filaments, oxidized polyacrylonitrile fibers and, optionally, one or more strengthening fibers.
2. The Relevant Technology
Fire retardant clothing is widely used to protect persons who are exposed to fire, particularly suddenly occurring and fast burning conflagrations. These include persons in diverse fields, such as race car drivers, military personnel and fire fighters, each of which may be exposed to deadly fires and extremely dangerous incendiary conditions without notice. For such persons, the primary line of defense against severe burns and even death is the protective clothing worn over some or all of the body.
Even though fire retardant clothing presently exists, such clothing is not always adequate to compensate for the risk of severe burns, or even death. Due to the limitations in flame retardance and heat resistance of present state of the art of flame retardant fabrics, numerous layers are typically worn, often comprising different fibrous compositions to impart a variety of different properties for each layer.
In view of the foregoing, there has been a long-felt need to find improved yarns, fabrics and other fibrous blends having better fire-retardant properties, higher heat resistance, lower heat transference, improved durability when exposed to constant heat or bursts of high heat, together with adequate strength and abrasion resistance, improved softness, better breatheability, improved moisture regain, increased flexibility and comfort, and other performance criteria. Examples of improved yarns, fabrics and other fibrous blends are disclosed in U.S. Pat. Nos. 6,287,686 and 6,358,608 to Huang et al., and U.S. Pat. No. 4,865,906 to Smith, Jr.
Even though the Huang et al. and Smith patents disclose fire retardant yarns, fabrics and other blends having a high Limiting Oxygen Index (xe2x80x9cLOIxe2x80x9d) and Thermal Protective Performance (xe2x80x9cTPPxe2x80x9d), additional strength and cut resistance may be necessary for certain applications, such as in the manufacture of gloves, clothing and other articles of manufacture that require high tensile strength, cut resistance and durability. Thus, it would be a further advancement in the art to provide yarns, fabrics and other heat resistant, fire retardant blends such as those disclosed in Huang et al., but which had greatly increased tensile strength, cut resistance, and even higher abrasion resistance and durability.
Such fire retardant yarns, fabrics, and other fibrous blends are disclosed and claimed herein.
The present invention encompasses novel yarns, fabrics, and other fibrous blends having high fire retardance, heat resistance, tensile strength, cut resistance, and durability. The yarns, fabrics, and other fibrous blends within the scope of the present invention include one or more fire retardant and heat resistant strands in combination with one or more high strength or strengthening filaments (e.g. metallic filaments). In a preferred embodiment, the heat resistant and fire retardant strands will comprise a significant concentration of oxidized polyacrylonitrile (e.g., oxidized polyacrylonitrile fibers and/or filaments), either alone or in combination with one or more strengthening fibers. Preferred strengthening filaments are made from stainless steel.
The high strength and cut resistant fire retardant and heat resistant yarns of the invention can be woven, knitted, or otherwise assembled into an appropriate fabric that can be used to make a wide variety of articles of manufacture. Examples include, but not limited to, clothing, jump suits, gloves, socks, welding bibs, fire blankets, floor boards, padding, protective head gear, linings, cargo holds, mattress insulation, drapes, insulating fire walls, and the like.
In addition to having greatly increased fire retardant and heat resistant properties, as well as tensile strength, cut resistance and high durability, the fabrics manufactured according to the present invention are typically much softer and flexible, and have a more comfortable feel, compared to the industry standard fire retardant fabrics. They also are more breathable and have superior water regain compared to the leading fire retardant and heat resistant fabrics presently on the market.
The yarns, fabrics and other fibrous blends according to the invention combine the tremendous fire retardant and heat resistant characteristics of oxidized polyacrylonitrile (either alone or in combination with strengthening fibers) with relatively high strength filaments to provide materials high in tensile strength, cut resistance other desirable properties. In a preferred embodiment, oxidized polyacrylonitrile fibers are advantageously carded or otherwise formed into one or more threads, which are twisted or otherwise combined with one or more metallic filaments to form high strength, cut resistant, abrasion resistant, heat resistant, and fire retardant yarns. The metallic filaments include, but are not limited to, stainless steel, stainless steel alloys, other steel alloys, titanium, aluminum, copper, and other metals or metallic blends. In addition to, or instead of, metallic filaments, other strengthening filaments can be used, such as high strength ceramic filaments (e.g., based on silicon carbide, graphite, silica, aluminum oxide, other metal oxides, and the like), and high strength polymeric filaments (e.g., p-aramides, m-aramides, nylon, and the like). Fiberglass can also be used, although it is typically blended with other strengthening filaments or fibers in order for the final yarn to have adequate strength.
The heat resistant and fire retardant strands, in addition to including oxidized polyacrylonitrile, may advantageously include one or more strengthening fibers in order to increase the tensile strength, abrasion resistance and durability of the strands compared to heat resistant and fire retardant strands made solely of oxidized polyacrylonitrile. xe2x80x9cStrengthening fibersxe2x80x9d include, but are not limited to, polybenzimidazole (PBI), polyphenylene-2,6-benzobisoxazole (PBO), modacrilic, p-aramid, m-aramid, polyvinyl halides, wool, fire resistant polyesters, fire resistant nylons, fire resistant rayons, cotton, and melamine fibers. In addition to adding abrasion resistance and other strengthening properties, many strengthening fibers (e.g. PBI, PBO, modacrilic, p-aramid, m-aramid, fire resistant polyesters, fire resistant nylons, and fire resistant rayons) can also impart fire retardance and heat resistance.
Oxidized polyacrylonitrile fibers and the strengthening fibers may be carded separately into respective unblended threads that are later twisted or spun together to form a mixed strand, or they can be carded together to form a blended thread. One or more fire retardant and heat resistant strands or threads are then intertwined or otherwise joined together with one or more high strength filaments to form a yarn of increased strength, cut resistant and durability compared to yarns that do not include such filaments.
In general, the quantity of strengthening filaments relative to the fire retardant and heat resistant threads can be adjusted in order to tailor the resulting yarn to have a desired tensile strength, cut resistance, and durability for a desired application. Thus, even yarns containing high concentration of oxidized polyacrylonitrile fibers that are generally too weak to be used in the manufacture of fire retardant and heat resistant fabrics are greatly strengthened with a small percentage of one or more metallic filaments, and fabrics manufactured therefrom have been found to be surprisingly strong.
In general, it is preferable for the inventive yarns according to the invention to include strengthening filaments in an amount in a range from about 2% to about 80% by volume of the yarn. More preferably, the inventive yarns will include strengthening filaments in an amount in a range from about 5% to about 50% by volume of the yarn, and most preferably in a range from about 10% to about 40% by volume of the yarn.
The inventive yarns will preferably include fire retardant and heat resistant strands in an amount in a range from about 20% to about 98% by volume of the yarn, more preferably in a range from about 50% to about 95% by volume of the yarn, and most preferably in a range from about 60% to about 90% by volume of the yarn.
As stated above, the fire retardant and heat resistant strands used to form the inventive yarns, fabrics or other fibrous blends according to the invention may consist solely of oxidized polyacrylonitrile (i.e., essentially 100% by weight of such fire retardant and heat resistant strands) or they may include a blend of oxidized polyacrylonitrile and one or more strengthening fibers to provide additional strength and abrasion resistance to the resulting mixed threads. When a blend of materials is used to make fire retardant and heat resistant threads, it is preferable for the threads to include oxidized polyacrylonitrile in an amount in a range from about 5% to about 99% by weight of the thread, more preferably in a range from about 40% to about 97% by weight, and most preferably in range from about 60% to about 95% by weight of the thread.
Similarly, when the fire retardant and heat resistant strands used to form the inventive yarns include strengthening fibers in addition to oxidized polyacrylonitrile fibers, the strengthening fibers are preferably included in an amount in a range from about 1% to about 95% by weight of the fire retardant and heat resistant threads, more preferably in a range from about 3% to about 60% by weight, and most preferably in an amount in a range from about 5% to about 40% by weight of the threads.
By optimizing the quantity of oxidized polyacrylonitrile relative to the quantity of the strengthening filaments and, optionally, strengthening fibers, it is possible to obtain yarns, fabrics, and other fibrous blends that possess superior fire retardant properties, higher heat resistance, lower heat transference, and improved durability when exposed to constant heat or bursts of high heat, together with adequate strength and abrasion resistance, improved softness, better breatheability, improved moisture regain, increased flexibility and comfort, and other performance criteria compared to conventional fire retardant fabrics presently available in the market.
The fire retardant and heat resistant strands and strengthening filaments can be joined together to form a yarn using any yarn-forming methods known in the art. For example, one or more strengthening filaments, being less fire retardant and heat resistant, may comprise the core, while one or more fire retardant and heat resistant strands can be wrapped or wound around the filament core. Alternatively, the fire retardant and heat resistant strands and strengthening filaments can be braided or twisted together as desired.
These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.